decapod | crustacean | Britannica.com crustacean 3-22-2013 Alternative Title: Decapoda Decapod, (order Decapoda), any of more than 8,000 species of crustaceans (phylum Arthropoda) that include shrimp, lobsters, crayfish , hermit crabs, and crabs. Masked crab (Corystes cassivelanus), Belgian coast. Hans Hillewaert The presence of five pairs of thoracic legs (pereiopods) is the basis for the name decapod (from the Greek meaning “10 legs”). Members of the order exhibit great diversity in size and structure. The macrurous (shrimplike) species, which can be as small as 1 cm (0.5 inch), have elongated bodies with long abdomens, well-developed fan tails, and often long, slender legs. The brachyurous (crablike) types, which in the case of spider crabs can have spans of almost 4 metres ...

(100 of 840 words) MEDIA FOR: Decapoda Investigation and Introduction Shellfish, a word colloquially used to describe edible marine animals, has a controversial and conflicting English lexicographic definition that varies in various English speaking countries such as Canada, United States, New Zealand, Australia and United Kingdom. Professor Andrew Pawley, at the Research School of Pacific and Asian Studies at the Australian National University noticed this inconsistency and conducted an informal survey based on 100 individuals from Australia, North America and New Zealand to put an end to this definition disparity (Pawley, 2004). At the end of the study, Professor Pawley redefined the word shellfish with consideration to the word variances and came up with the following definition (Pawley, 2004): Shellfish n. Applied to a variable range of small edible invertebrates that live in water and that are eaten. (For most speakers not a category of fish.) The most common variant meanings are: Molluscs with shells, that live in water. (Usual in NZ, common in Australia and UK, rare in USA.) Molluscs and crustaceans.

(Usual in USA, common in UK and Australia, rare in NZ, except among professionals in the food trade.) Edible bivalves only. (Occasional in Australia and USA.) Crustaceans only. (Occasional in Australia.) Food consisting of these animals. Extended by some to all members of the zoological classes listed under 1, whether eaten or not. (UK, USA, Australia, NZ.) Contrary to the common North American description of the term shellfish, for the purpose of this investigation, we consider the order Decapoda to be strictly a non-shellfish. Although decapods are more commonly known for their commercial purpose as seafood, there is much more to decapods than meets the stomach. This treehouse will cover a variety of information about decapods and will ultimately answer why they are one of the most unique and non-“shellfish” orders of marine metazoans out there.

Classification The word Decapoda, created by the combination of the Greek words deka meaning ‘ten’ and pous meaning ‘foot’ is used to classify a variety of familiar marine animals such as shrimp, lobster, crayfish, hermit crabs and crabs (AskOxford.com, 2004). The classification of the order Decapoda and overall the class Crustacea have always been a difficult task due to their morphological diversity and the lack of a fossil record amongst its species (Martin and Davis, 2001). Classification of Crustacea is based on a variety of methods including the use of cladistics, molecular systematics, developmental genetics, sperm morphology, larval morphology and fossil record (Martin and Davis, 2001). The groups contained in the order Decapoda are presented as follows : Major Groups in Decapoda (Salmon, 1983) Natantia (shrimps and prawns): Consists of 2000 species of crustacea. Found in depths that range from shallow to deep waters. Can be found in both salt and fresh water. Specialized strong and rapid swimming.

Palinura (spiny lobsters): Consists of 130 species of crustacea. Astacura (lobsters and crayfishes) Brachyura (crabs): Largest group of decapods containing 4500 species. Highly specialized morphologically with reduced antennae, small abdomen tucked under thorax, and a pair of chelae. Anomura (mole crabs, hermit crabs, and coconut crabs): Consists of 1400 species. Abdomen is asymmetrical and well-developed. Last pair of walking legs are reduced in size and are oriented on the dorsal side or covered by the carapace. Group known for mimicking other decapod species in their form, ecology and behaviour. Anatomy Decapoda have many shared traits. One trait, which is implied in their name, would be their ten legs. These consist of the last five pairs of the eight pairs of thoracic appendages. Decapods are also noted for their hard exoskeleton, segmentation, and jointed appendages, which are used for sensory reception, feeding, locomotion, and defense.

The body of a decapod is divided into several distinct morphological and functional regions called tagmata. The more basal decapods have less tagmatized body plans. As this morphology is thought to be similar to that of the last common mandibulate ancestor, understanding these underlying features and their development becomes pivotal for understanding the evolution of the Decapoda. Gills are an interesting decapod feature with an extensive surface area that is used for gas exchange with the surrounding water. These gills are located on each appendage from the second maxilliped to the fifth pereiopod. The auxiliary heart found in decapods is a notable feature. It is located at the anterior end of the dorsal median artery before the artery branches to supply the supraesophageal ganglion (the decapod brain), and the peripheral oculomotor and visual systems. Also referred to as the cor frontale, the auxiliary heart is controlled and integrated with several other systems. The auxiliary heart is significant due to its adaptation. Decapods possess open venous systems, an inflexible carapace, and a highly variable volume of the stomach, which all influence the blood pressure. The auxiliary heart allows decapods to better maintain blood pressure levels.

The body of a decapod contains nineteen segments, which may contain a pair of appendages, and can be divided into two main divisions: the cephalothorax (head and thorax/pereon) and the pleon (abdomen). The following is a breakdown of these features (listed from anterior to posterior). Cephalothorax Pereon / Thorax First, second, and third maxillipeds The maxilliped appendages are modified to function as mouthparts. In more basal decapods, they are very similar to the pereipods. First, second, third, fourth, and fifth pereiopods Pereiopods are the primary walking legs, they are used for gathering food, and bear the sexual organs found in the fifth pereiopod in the male and the third pereiopod in the female. The gills are found in the second maxilla to the fifth pereiopod. Chelipeds are those pereipods that are armed with a chela or a claw.

Pleon / Abdomen First, second, third, fourth, and fifth pleopods/swimmerets Uropods Telson Pleopods or swimmerets are used for swimming, brooding eggs (except for Natantia), catching food, sweeping food into the mouth, and sometimes bearing gills. In the males of some taxa, the first one or two pairs of pleopods are referred to as gonopods as they are specialised for fertilisation. The tail fan is responsible for steering while swimming. Located at the posterior end of the pleon, the tail fan is composed of a pair of biramous uropods and the telson. The anus of the Decapod is located within the telson. In crabs and other carcinised decapods, the pleon is folded under the cephalothorax Click on an image to view larger version & data in a new window The general anatomical features of a Decapod, using Palinura as a model. Reproduction Decapods are egg-laying invertebrates, mainly with seperate sexes. A change of sex during the lifetime of an individual is a regular occurence in some Dendrobranchiates.

In Pandalus montagui, some individuals begin life as males but then transform into functional females after 13 months. Males of crab and lobster species are usually larger than the females and possess much larger pincers. The males also possess clasping organs used to hold the female during mating. Appendages can also be modified to assist in the sperm transfer process. The sperm is often encased in a spermatophore, and the first and second abdominal appendages are modified to transfer these spermatophores. Methods for brooding eggs vary among the decapods as follows: Suborder: Dendrobranchiata Consists of shrimp and prawns. Reproduce by releasing eggs into the water. Eggs then hatch as a nauplius, a larva consisting of a head and a telson. Suborder: Pleocyemata Includes crabs, lobsters, and crayfish. Eggs are attached to abdominal appendages where special setae secrete a cement that binds the eggs to the setae. Larvae hatch in a more developed stage than a nauplius. The Larvae The larva of decapods and of many other crustacea is the nauplius.

It consists of an unsegmented body with only a head, telson, three pairs of appendages (antennules, antennae, and mandibles), and a simple nauplius eye. Once the body is more elongated and segmented, the nauplius is called a metanauplius. The nauplius larva makes an important evolutionary statement for the crustacea as they start to diverge from other arthropods (Encyclopaedia Britannica, 2005). Behaviour and Mechanisms Grooming Grooming is a common behaviour found in many crustaceans as a form of maintenance to rid their bodies of epizoic growth and particulate buildup (Bauer, 1981). In the Decapoda, this behaviour is extremely crucial and helps prevent the growth of foreign organisms on their body surfaces, loss of olfaction hairs, clogging of gills and embryo mortality. Grooming within the decapod crustaceans involves the use of chelipeds and the setal brushes at the tips of their walking legs.

The most frequently groomed areas of the body include the sensory and respiratory structures that consist of the antennules, antennae, and gills (Bauer, 1981). Mechanisms of Grooming Preening involves the use of the third maxilipeds. It is the most common cleaning behaviour found amongst the order of Decapods. Antennal Flagellum Grooming: Preening method most commonly found in cardean shrimp. It involves the cleaning of the long chemotactile antennal flagella with setal brushes located on the first pair of chelipeds. Gill Cleaning: The enclosure of gills within the branchial chamber is a unique morphological feature found in the Decapod order of crustaceans. The gill chamber is flushed by reversing the respiratory current or is cleaned by the use of setae. General Body Grooming: Involves the brushing of the exoskeleton (comprised of carapace, thoracic sternites, abdominal pleurites and sternites, and body appendages) and picking at areas in between appendages and body segments.

Alternatives to Grooming Some decapod species use other mechanisms other than grooming to maintain their body surface cleanliness. Some alternative methods include: Burrowing into deep sediment. Reproductive Behaviour Attraction Cues In most decapod species, the males and females live separately from each other and pair-up as adults only to mate (Salmon, 1982). Since males and females are separated by vast spatial distances they rely on a combination of chemical, visual and acoustic signals to attract a mate (Salmon, 1982). Some of these signals are further discussed below. Chemical Signals. This type of attraction involves sex pheromones which are the most commonly used signal in aquatic decapods (Salmon, 1982). The use of pheromones is most evident in decapod species where female molting and mating are closely linked temporally (Salmon, 1982). Visual Signals. This type of attraction occurs most commonly in close-range courtship amongst aquatic species or long-range courtship amongst land species of decapods (Salmon, 1982).

Visual signals may involve a "dance" or repetitive movement of a body part, such as "waving" (Salmon and Hyatt, 1983). Acoustic Signals. This type of attraction occurs predominatly in ghost and fiddler crabs (Salmon and Hyatt, 1983). These acoustic "calls", that only occur during the mating season, are strictly produced by males to indirectly attract females (Salmon and Hyatt, 1983). Natantia (shrimps and prawns) Chemical attraction signals released when the female molts to signify that she is sexually receptive and ready to mate. Palinura (spiny lobsters) Chemical attractin signals released during female molting to attract male mate. Fertilization occurs when a male first places a spermatophore on the female's sternum, her unfertilized eggs will pass over the area and become fertilized. Astacura (lobsters and crayfishes) Courting pattern varies greatly between species. Courtship behaviours involve a combination of pheromones and molting depending on the species. Brachyura (crabs) Species attract mates using chemical signals (e.g. sex pheromones).

Courtship behaviour lasts longer compared to other decapod species. Once paired together, the male will service the female and assist in her molting. During this process, the male will protect the female from predators and other males that may try to copulate with her. Terrestrial Species Species attract mates through visual and sound courtship cues. Well-known example of visual courtship is that of the male fiddler crabs (genus Uca) where they "wave" their enlarged chelae to attract females to their burrow. This repetitive action has also been shown to repel other males. Anomura (mole crabs, hermit crabs and coconut crabs) Mole crab males experience neoteny and are physically smaller than females. This sexual size dimorphism allows the males and females to share the same niche therefore allowing easier access to mates during the mating season. Hermit crabs exhibit courtship behaviours that involve a combination of actions such as stroking, jerking, and shell-rocking. Sexual Selection Decapods are polygynous and sexually dimorphic (Salmon and Hyatt, 1983).

Males tend to be physically bigger and this allows competitive behaviour between males for access to females (Salmon and Hyatt, 1983). Females on the otherhand are selective in choosing their mates and base their decisions on the male's ability to acquire resources and the male's ability to dominate other males (Salmon and Hyatt, 1983). Feeding Most decapods are scavengers, feeding mostly on detritus, but it is also known that if small live fish come too close, decapods with chelae may thrust their claws after them. Tools It is well known that some animals such as the Monkeys use tools, e.g., sticks to get something out of reach. However, it is only well known in the scientific community that some decapods will use tools as well! There are at least two crabs that carry living sea anemones to be used as weapons. Lybia tessellata and Lybia leptochelis are two species that seem to be most unhappy without at least one sea anemone. The sea anemone Triactis producta seems to always be the anemone of choice as it is bestowed with nettle-cells.

Any small animal that comes into contact with these cells would likely soon perish. The claws of Lybia are especially adapted for grasping the sea anemone's fleshy body. If live fish, amphipods, or any other of the like come too close, the crab thrusts out the sea anemone. The victim, if struck, will fall to the sea floor where it will be picked up by the crab. Hermit crabs have also been seen keeping a sea anemone on their shell for protection. Locomotion Locomotion of crustaceans is very important in a variety of activities including for feeding, courtship displays, grooming and walking (Evoy and Ayers, 1982). The movement of crustacean limbs involves a network of muscles, neurons and appendages used to coordinate the movement of appendages that make locomotion possible (Evoy and Ayers, 1982). Muscles within crustaceans are involved in different types of movements where the muscles used can be classified as being synergistic or antagonistic (Evoy and Ayers, 1982).

Synergistic muscles involve a single type of movement, such as walking forward (Evoy and Ayers, 1982). While anatagonistic muscles involve a variety of movements such as sideways walking, swimming, or courtship displays (Evoy and Ayers, 1982). The jointed appendages supported by muscles are highly specialized to various types of movements (Lochhead, 1961). Also, Decapod appendages are arranged in a fashion where their legs hang to allow maximum stability for their unique morphology (Lochhead, 1961). This appendage arrangement allows legs located on the posterior region to be highly specialized in pushing, while legs in the anterior region are specialized in pulling (Lochhead, 1961). Legs that are intermediate can be used for either pushing or pulling (Lochhead, 1961). Types of Locomotion Swimming. There are two forms of swimming associated with decapod crustaceans (Evoy and Ayers, 1982).

One that involves rhythmic extension and flexing of muscles contained in the abdomen to allow jet propulsion through the water (Evoy and Ayers, 1982). The other form of swimming involves rhythmic sculling movements of the appendages (Evoy and Ayers, 1982). The mechanisms involved in swimming are expanded further below (Lochhead, 1961): Using appendages to act as oars Using appendages to create vortexes by rotational beating of the water Using appendages to act like propellers which move at right angles to the path of motion Beating the abdomen therefore driving the animal forward Flexing the abdomen and fanning the tail Walking Forward. The forward walking motion for decapods involves the coordinated pushing and pulling of paired legs moving at a rhythmic out-of-phase pattern (Lochhead, 1961). Walking Sideways. This type of locomotion is commonly found among crustaceans that have fewer than six pairs of legs (Lochhead, 1962). This special physiological adaptation allows individuals to exhibit less instances of appendages overlapping during walking (Lochhead, 1961).

Sideways walking also involves the coordinated flexing and extending of legs at either sides of the body (Lochhead, 1962). Cell Division and Cleavage Patterns Cell cleavaging is an important and crucial step in the development of any animal especially during embryogenesis. This ubiquitous process is different in many metazoan groups and ultimately can be used to classify various groups of metazoans. During embryo development, the decapod crustaceans undergo protostomic development where the mouth is the first developmental opening in the blastopore. The second opening then develops into the anus of the embryo. This protostomic development is also commonly found in other arthropods and in other groups such as annelids and mollusks. Most malacostracan crustaceans undergo superficial cleavage, however the Decapoda undergo complete holoblastic cleavage. Due to the spiral holoblastic cleaving of decapod cells, they characteristically have larger eggs than other crustacea, alongside with a greater yolk mass, intralecithal cleavage, blastoderm formation and epimorphic later development (Anderson, 1973).

This characteristic spiral cleaving is different from the spiral cleaving noticed in annelids (Anderson, 1973). Biogeography Dispersion and vicariance events are known to be responsible for the creation of faunal provinces or regions with similar groups of organisms. Physical barriers, such as ocean currents and land masses can seperate organisms allowing them to evolve away from each other. Fauna found in close proximities have been noted as being more similar (Feldman and McLay, 1993) Different vicariance effects influencing the Decapoda Decapod faunas of eastern and western South America are noticeably different from each other due to barriers such as ocean current patterns. In the early Eocene, a strong similarity was demonstrated in decapod faunas between New Zealand and Antarctica. This similarity disappeared over time as New Zealand diverged from Antarctica due to tectonic movement. A noticeable similarity between the decapoda of the North American east coast and those of southern Europe suggests ocean currents as a dispersal mechanism from east to west across the Atlantic A Tethyan distribution pattern is evident in decapods due to similarities between Eocene faunas of Europe and Japan.

The tethyan trench formed 200 million years ago in the early Jurassic and is likely responsible for moving Africa and India towards Eurasia. Decapoda of the North Pacific region can be assigned to five major origins. These are: a North Pacific origin an orgin from the high southern latitudes an amphitropical origin Domestication of Decapoda Decapods are becoming more and more popular as pets in aquaria. More stores are now carrying them as popularity increases. Natantia Shrimp are kept as pets in aquaria so they will feed on detritus or algae, or they may simply be kept as ornamental pets. The shrimp that are kept as pets include: Yamato Numa Ebi/Caridina spp., Ghost/Grass (Paleomonetes sp.), Wood/Singapore (Atyopsis sp.) , Rock/Mountain, Bumble Bee (Atydea sp.), Macrobrachium, and Neocaridina sp. Brachyura True crabs are becoming more and more popular acquarium pets, feeding on dried blood worms, brine shrimp, or dried flake food.

Crabs that are kept as pets include: Freshwater Gold Fiddler Crabs, Freshwater Red Claw Crabs. Anomura Includes hermit crabs, which have been kept as pets for a relatively long time. Omnivorous or herbivorous and are useful in aquaria as scavengers, eating debris and algae Will switch shells when provided with a larger one Popular hermit crab species ket as pets include the Caribbean hermit crab (Coenobita clypeatus) and the Pacific hermit crab (Coenobita compressus) Less common species kept as pets include Coenobita brevamanus, Coenobita rugosus, Coenobita perlatus and Coenobita cavipes. Pleocyemata Will eat shrimp pellets, vegetables, tropical fish food, algae wafers, and eve small fish. Crayfish kept in aquaria include red crayfish (Cherax quadricarinatus) and blue crayfish (Procambarus alleni). Decapod Records Largest Decapod: : Macrocheira kaempferi, the giant spider crab.

Individuals can reach a diameter of 12-14 inches (30.5-35.6cm), with a claw span of 8-9 feet (2.4-2.7m). There is a report of a crab weighing 14 pounds and a claw span of 12 feet (3.65m). Smallest Crab: The pea crabs of the Pinnotheridae are approximately 0.25 inches (0.635cm) across the shell. Heaviest Decapod: Homarus americanus, Atlantic Lobster. Records exist of individuals weighing over twenty pounds. The largest record, however, belongs to a lobster weighing 42 pounds and 7 ounces. This lobster was caught in 1934 and bestowed with the nickname "Mike." References Amphibious Land Crabs. Shrimps, Crabs, and Crayfish. < ~mainFrame> Anderson, D.T. 1973. Embryology and Phylogeny in Annelids and Arthropods. Pergamon Press Press Ltd, New York, pp 128-179. AskOxford.com. Decapod. 2007.

. [accessed 2007 April 27] Beltz, Barbara S. Distribution and Functional Anatomy of Amine-Containing Neurons in Decapod Crustaceans. 1999 Bauer, R.T. 1981. Grooming behavior and morphology in the decapod crustacea. Journal of Crustacean Biology. 1:153-173. Biggest, Smallest, Fastest, Deepest: Marine Animal Records. OceanLink, 2007. Crustaceans. Encyclopaedia Britannica ï¿½ Macropaedia Knowledge in Depth ï¿½ Volume 16. 2005. p.842 Decapod Anatomy. Wikipedia, 2007. Evoy, W.H. and Ayers, J. 1982. Locomotion and Control of Limb Movements. In: The Biology of Crustacea: Neutral Integration and Behavior (Sandeman, D.C. and Atwood, H.L. eds.) Academic Press, New York, 61-104. Harper, Douglas. Online Etymology Dictionary. Hertzler, P. L.

2005. Cleavage and gastrulation in the shrimp Penaeus (Litopenaeus) vannamei (Malacostraca, Deacapoda, Dendrobranchiata). Arthropod Structure & Development. 34:455-469. Lochhead, J.H. 1961. Locomotion. In: The Physiology of Crustacea: Sense Organs, Integration, and Behavior (Waterman, T.H. ed.) Academic Press, New York, 313-364. Martin, J.W. and Davis, G.E. 2001. An updated classification of the recent crustacea. Natural Science Series: History Museum of Los Angeles County. 39:1-132. Pawley, A. Are crustaceans shellfish? A whiff of scandal in English lexicography. June 2004. . [accessed 2007 April 30] Roach, John. Decoding Spiny Lobstersï¿½ Violin-Like Screech. National Geographic News, 2004. < Salmon, M. 1983.

Courtship, mating systems, and sexual selection in decapods. In: Studies in Adaptation: The Behavior of Higher Crustacea (Rebach, S. and Dunham D., eds.) John Wiley & Sons, Inc, Canada, pp. 143-169. Salmon, M. and Hyatt, G.W. 1983. Communication. In: The Biology of Crustacea: Behavior and Ecology (Vernberg, F.J. and Vernberg, W.B. eds.) Academic Press, New York, 1-40. Schmitt, Waldo L. 1965. Crustacean Habits and Homes. Crustaceans. The University of Michigan, 148-149. Scholtz, Gerhard. 2004. Evolutionary Developmental Biology of Crustacea. Crustacean Issues 15. A.A. Balkema Publishers. 43-91 Schweitzer, Carrie E. Paleobiogeography of Cretaceous and Tertiary Decapod Crustaceans of the North Pacific Ocean. The Paleontological Society, 2001 Steinacker, A.

The Anatomy of the Decapod Crustacean Auxiliary Heart. University of California, 1978. Zimmerman, Todd. True Crabs ï¿½ Infraorder Brachyura, 2000. < Learning Information Decapod Crabs Decapod Crabs Along the Eastern Warm Temperate Zone in south-eastern Australia on rocky ocean shores, there are many types of crab from different families. Typical shore crabs belong to two major groups; the Grapsid Shore Crabs and the tall-eyed Ocypode Crabs. Grapsid Shore Crabs - Grapsidae The Grapsids have invaded the largest number of shore habitats. They may be distinguished by their broad fronts, short eyes and almost square-shaped carapace. Some grapsids can leave the water for long periods of time. As the deoxygenated and carbon dioxide loaded water is expelled from the gill chambers, it is spread over spongy areas on either side of the mouth where it picks up fresh oxygen. Appendages at the entrance of the gill cavity near the base of the claws (chelipeds) drives the oxygen recharged water back to the gills.

Most grapsids have equal-sized chelae (claws), unless one has been broken off and is regrowing. Male grapsids usually have much larger chelae than females of the same species. Some grapsid shore crabs which are found along our shores are: Ocypodid Shore Crabs - Ocypodidae The other major group of shore crabs are the Ocypodids, These are the Ghost Crabs and Fiddler Crabs and relatives. They are mostly all tall-eyed, with the bases of their eyes close together at the front of the carapace. Ocypodid crabs live on sandy beaches, mudflats and in mangrove swamps. They are active burrowers and many live in colonies. The male Ghost Crabs and especially the Fiddler Crabs have unequal sized chelae. Ocypodids are not normally found on rocky ocean shores. Spider Crabs - Majidae These Majidae crabs are commonly known as the Spider Crabs. The seaweed crabs of this family are covered with long hooked hairs, which allow the crab to snip off living pieces of algae and attach them to the hairs.

A decorated seaweed crab with algae, sponges and other marine growths is excellently camouflaged. It only gives itself away when it moves. One seaweed crab found in the intertidal zone in south-eastern Australia is the: Black Fingered Crabs - Xanthidae The black-fingered crabs are the largest group of crabs in Australian seas. Xanthids are very common in tropical waters, especially on the Great Barrier Reef. Most members of the group are almost oval in shape, being slightly wider than long. The distinguishing feature of the group, is the dark coloured fingers of the chelae. The most common black-fingered crab on rocky ocean shores in south-eastern Australia is the: Swimming Crabs - Portunidae The portunid swimming crabs have a broad carapace and flattened hind legs which form swimming paddles and sometimes digging spades. None of the portunids come out onto the shore, but they do enter shallow water to hunt for live food. The most common estuarine swimming crab is the Blue Swimmer Crab, Portunus pelagicus.

On the rocky ocean shore one of the most attractive crabs is the: Regrowth of Limbs Decapod crabs can regrow their limbs if they are broken off. In fact there is a special "weakness plane" across the leg, so that if a predator grasps the limb, the leg breaks off, and special muscles contract and pinch off the nerves and stem the loss of fluid. It takes about six or so moults to regrow a severed limb. For more information on Crustaceans visit MESA Crustaceans Oldest Crabs Found? Spider Crab Species In Fossil Reef Date Back 100 Million Years, Scientists Say | The Huffington Post Oldest Crabs Found? Spider Crab Species In Fossil Reef Date Back 100 Million Years, Scientists Say 02/04/2013 11:24 pm ET By: Jeanna Bryner Published: 02/04/2013 11:37 AM EST on LiveScience The remains of eight new species of crustaceans, including the oldest known spider crabs that lived 100 million years ago, have been uncovered in a fossil reef in northern Spain, scientists report.

The fossils were found in the abandoned Koskobilo quarry alongside other species of decapod crustaceans (a group that includes crabs, shrimp and lobsters ). The two oldest-known spider crabs , named Cretamaja granulata and Koskobilius postangustus, are much older than the previous record holder, said study author Adiël Klompmaker, a postdoctoral researcher at the Florida Museum of Natural History at the University of Florida. "The previous oldest one was from France and is some millions of years younger," Klompmaker told LiveScience, referring to the spider crabs. "So this discovery in Spain in quite impressive and pushes back the origin of spider crabs as known from fossils." C. granulatawas about 0.6 inches (15 millimeters) long and showed distinctive features to suggest it was a spider crab, including two diverging spines coming out of its rostrum (the extended portion of the carapace, or shell, in front of the eyes) and a somewhat pear-shaped carapace. The fossil spider crab also sported spines on its sides at the front of the body.

[ See Photos of the Ancient Spider Crabs ] The reef where they were found seems to have vanished shortly after these creatures lived. "Something must have happened in the environment that caused reefs in the area to vanish, and with it, probably many of the decapods that were living in these reefs," Klompmaker said. "Not many decapods are known from the time after the reefs disappeared in the area," added Klompmaker, who details the findings in a forthcoming issue of the journal Cretaceous Research. With a team of researchers from the United States, the Netherlands and Spain, Klompmaker collected fossils in the Koskobilo quarry in 2008, 2009 and 2010. "We went there in 2008, and in the first two hours found two new species," Klompmaker said in a statement.

"That's quite amazing — it just doesn't happen every day." With the new findings, some 36 decapod species are known to have existed at the abandoned quarry, making it one of the most diverse localities for decapods during the Cretaceous period (145 million to 66 million years ago), Klompmaker said. The researchers also found there were more diverse ancient decapods living within the reefs — where they fed, mated and sought shelter — than in other parts of the ocean. Another newfound crab, called Albenizus minutus, from the quarry in northern Spain. The crab was teensy, with a length of just 3.2 millimeters, not including its rostrum (the extension of the shell in front of the eyes). "One of the main results of this research is that decapod crustaceans are really abundant in reefs in the Cretaceous," Klompmaker wrote in an email.

"The presence of corals seemed to promote decapod biodiversity as early as 100 million years ago and may have served as nurseries for speciation." Last year, Klompmaker reported finding fossils of tiny lobsters huddled together in the seashell of an extinct mollusk known as an ammonoid. The "embracing" lobsters, found in a rock quarry in southern Germany, suggested these fearsome-looking crustaceans were sociable as long ago as 180 million years, when the little crustaceans lived. "This is the oldest example of gregarious behavior for lobsters in the fossil record — and not just lobsters but the entire group of decapods, which includes lobsters, crabs and shrimp," Klompmaker, who was at Kent State University, said at the time. "What this tells us is that this type of behavior of grouping together may have been very beneficial early on in the evolution of these crustaceans." Klompmaker was also part of a team that discovered a new hermit crab at the same quarry, naming it after Michael Jackson (Mesoparapylocheles michaeljacksoni), as it was found around the time the singer died.

Follow LiveScience on Twitter @livescience . We're also on Facebook & Google+ . Shellfish information-Crabs-Barnegat Bay Ghost Crab Ocypode quadrata Ghost crabs belong to the Family Ocypodidae (fiddler crabs and ghost crabs) Adults are grayish or the color of straw, and about 2 inches wide at maturity. Like fiddler crabs, they are terrestrial and need to return to the water periodically to moisten their gills . Their compound eyes are on stalks and can swivel to give them 360° vision. Also called sand crabs, they are mostly nocturnal being active from dusk to dawn, scouring the beach looking for anything edible. Ghost crabs spend most of the daytime hours in burrows. The golf ball-sized entrance holes may be visible in the dry sand of the upper beach, or in the sand dunes. The burrows extend down 3-4 feet with a "turn-around" chamber at the end. They also use these burrows to hibernate in winter existing by storing oxygen in specialized sacs near their gills. Ghost crabs return to the water for a few reasons.

As mentioned above, they need to moisten their gills to breathe. Females with egg masses need enter the water to keep them moist and to release the young when they hatch. Running into the water is also a means to escape from a predator if the burrow is not accessible. Fun Fact - Ghost crabs are one of the fastest crustaceans capable of running up to 10 MPH and they can run forward, backward and sideways. Fun Fact - Like fiddler crabs, ghost crabs have one enlarged claw. Hermit Crabs Hermit Crabs are not true crabs, but are an intermediate form having a soft shrimp-like tail that is protected inside the snail shell. (like all crabs, they are decapods ) Unlike other crabs, the hermit crab has no exoskeleton , so for protection, it forces its vulnerable body into the curved chamber of an empty gastropod shell (or similar object) for protection. The four hind legs that appear to be missing have evolved into grippers that hold the crab inside the shell so strongly that you will tear the animal in half before you can extract it.

The claws are usually shaped so that together they will exactly block off the opening when the crab retreats inside. <click here or on image to enlarge> Hermit Crabs are always on the lookout for bigger and better shells, and when they find one they like, they quickly switch to see if is the right fit. Fun Fact - hermit crabs can be classified as marine hermit crabs and land hermit crabs. Marine crabs breathe through gills using the oxygen dissolved in water. Land crabs have a modified gill mechanism that absorbs oxygen from the humidity in the air. Long-Armed Hermit Crab Pagurus longicarpus Long-armed hermit crabs are marine crabs that inhabit the shorelines and muddy or sandy bottoms of Barnegat Bay They live in grass beds, from the low-tide line to the deeper waters of the bay. Their bodies are greenish-white or gray with pincers that are often gray with light brown stripe. The right pincer is larger than the left and is three times longer than it is wide. The long-clawed hermit lives in the shells of mud snails, oyster drills or periwinkles.

The body grows to about one inch (or less) The long-armed hermit crab is a scavenger which consuming edible material from the surfaces of sand grains and also a consumes larger pieces of detritus plant and animal material therefore , an omnivore . Credits Arthropods - 2 | Britannica.com Arthropods any member of the phylum Arthropoda, the largest phylum in the animal kingdom, which includes such familiar forms as lobsters, crabs, spiders, mites, insects, centipedes, and millipedes. Displaying 1 - 100 of 128 results acarid Acari or Acarida or Acarina any member of the subgroup of the arthropod class Arachnida that includes the mites and ticks. General features Size range and diversity of structure Some mites are as small as 0.1 mm (0.0039 inch) in length, while the largest... Agnostus genus of trilobites (an extinct group of aquatic arthropods) found as fossils in rocks of Early Cambrian to Late Ordovician age (those deposited from 540 to 438 million years ago).

The agnostids were generally small, with only two thoracic segments and... Ameura genus of trilobites (extinct arthropods) found as fossils in North America rocks dating from the Late Carboniferous to the Late Permian Period (from 318 million to 251 million years ago). Ameura is characterized by a well-developed cephalon (head) and... amphipod any member of the invertebrate order Amphipoda (class Crustacea) inhabiting all parts of the sea, lakes, rivers, sand beaches, caves, and moist (warm) habitats on many tropical islands. Marine amphipods have been found at depths of more than 9,100 m... arachnid Arachnida any member of the arthropod group that includes spider s, daddy longlegs, scorpion s, and (in the subclass Acari) the mite s and tick s, as well as lesser-known subgroups. Only a few species are of economic importance—for example, the mites...

arthropod any member of the phylum Arthropoda, the largest phylum in the animal kingdom, which includes such familiar forms as lobsters, crabs, spiders, mites, insects, centipedes, and millipedes. About 84 percent of all known species of animals are members of... Bagheera kiplingi species of jumping spider (family Salticidae) noted for its largely plant-based diet. The herbivorous nature of Bagheera kiplingi distinguishes it from all other spiders, which are almost exclusively carnivorous; a minority of species are known to supplement... barnacle any of more than 1,000 predominantly marine crustaceans of the subclass Cirripedia highly modified for sedentary life. There are about 850 free-living species (all marine) and about 260 species that are internal parasites of crabs and other crustaceans.... Bathyuriscus genus of trilobites (extinct arthropods) that provide a useful index fossil for the Middle Cambrian epoch of North America (520 to 512 million years ago).

In Bathyuriscus the head segment is well developed, and marginal spines are present. The tail region... black widow Latrodectus any of several species of black spider s distinguished by an hourglass-shaped marking on the abdomen. Black widows, especially L. mactans, are found throughout much of the world. The bite of the black widow often produces muscle pain, nausea,... blue crab (genus Callinectes), any of a genus of crustaceans of the order Decapoda (phylum Arthropoda), particularly Callinectes sapidus and C. hastatus, common edible crabs of the western Atlantic coast that are prized as delicacies. Their usual habitat is muddy... book lung form of respiratory organ found in certain air-breathing arachnid arthropods (scorpions and some spiders). Each book lung consists of a series of thin plates that are highly vascular (i.e., richly supplied with blood) and are arranged in relation to... branchiopod any of the roughly 800 species of the class Branchiopoda (subphylum Crustacea, phylum Arthropoda).

They are aquatic animals that include brine shrimp, fairy shrimp, tadpole shrimp, water fleas, and other small, chiefly freshwater forms. Branchiopods... brine shrimp (genus Artemia), any of several small crustaceans of the order Anostraca (class Branchiopoda) inhabiting brine pools and other highly saline inland waters throughout the world. Artemia salina, the species that occurs in vast numbers in Great Salt Lake,... brown recluse Loxosceles reclusa venomous light tan or yellow spider most common in the western and southern United States. It has a body length of about 7 mm (0.25 inch) and a leg span of about 2.5 cm (1 inch). On the front half of its body (the cephalothorax), it... Bumastus genus of trilobites (extinct arthropods) found in Europe and North America as fossils in rocks of Ordovician to Silurian age (between 408 and 505 million years old). Bumastus is very distinctive in form; the head and tail regions are smooth and very...

Calymene genus of trilobites (extinct arthropods) dating from the Ordovician Period (505 to 438 million years ago). Well known in the fossil record, Calymene remains have been found in which impressions or actual remains of appendages are preserved. Calymene... Cedaria genus of trilobites (extinct arthropods) that is a useful index fossil for Cambrian rocks and time (about 542 million to 488 million years ago). Cedaria was small, with a well-developed tail section and a prominent head section. centipede Chilopoda any of various long, flattened, many-segmented predaceous arthropods. Each segment except the hindmost bears one pair of legs. Centipedes generally remain under stones, bark, and ground litter by day. At night they hunt for and capture other... Ceraurus genus of trilobites (extinct arthropods) found as fossils in rocks of Ordovician period (505 to 438 million years ago) in Europe and North America.

Ceraurus is easily recognized by its unusual shape; two large spines occur at the end of the tail and... chigger Prostigmata the larva of any of approximately 10,000 species of mites in the invertebrate subclass Acari (the mites and ticks). The name is also erroneously applied to an insect better known as the chigoe, jigger, or jigger flea. Chiggers range in length... cirripede any of the marine crustaceans of the infraclass Cirripedia (subphylum Crustacea). The best known are the barnacles. Adult cirripedes other than barnacles are internal parasites of marine invertebrates such as crabs, jellyfish, and starfish, and have... clam shrimp any member of the crustacean order Conchostraca (subclass Branchiopoda), a group of about 200 species inhabiting shallow freshwater lakes, ponds, and temporary pools throughout the world. Clam shrimps are so called because their entire body is contained... comb-footed spider any member of the spider family Theridiidae (order Araneida).

The more than 1,000 species of comb-footed spiders are distributed around the world, and they include the black widow. The webs of theridiids consist of an irregular network of threads from... copepod Copepoda any member of the widely distributed crustacean subclass Copepoda. Copepods are of great ecological importance, providing food for many species of fish. Most of the 13,000 known species are free-living marine forms, occurring throughout the... crab any short-tailed member of the crustacean order Decapoda (phylum Arthropoda)—especially the brachyurans (infraorder Brachyura), or true crabs, but also other forms such as the anomurans (suborder Anomura), which include the hermit crabs. Decapods occur... crab spider Thomisidae family of spiders (order Araneida) that are crablike in shape and, like many crabs, often walk sideways or backward. The family, which is worldwide in distribution, contains many common species that live on the soil surface, in leaf litter,...

crayfish any of numerous crustaceans (order Decapoda, phylum Arthropoda) constituting the families Astacidae (Northern Hemisphere), Parastacidae, and Austroastracidae (Southern Hemisphere). They are closely related to the lobster. Over half of the more than 500... Crepicephalus genus of trilobites (extinct arthropods) useful as an index fossil for Upper Cambrian rocks in North America (dating 512 to 505 million years ago); it is a relatively common fossil and occurs over a wide geographic range but within a relatively narrow... crustacean any member of the subphylum Crustacea (phylum Arthropoda), a group of invertebrate animals consisting of some 45,000 species distributed worldwide. Crabs, lobsters, shrimps, and wood lice are among the best-known crustaceans, but the group also includes... crustacean louse any of various small aquatic invertebrates of the subphylum Crustacea (phylum Arthropoda) that are parasites of fish.

Crustacean lice include fish lice (subclass Branchiura), copepod fish parasites (subclass Copepoda), and amphipod and isopod fish parasites... Cryptolithus genus of trilobites (extinct arthropods) found as fossils in Europe and North America in the Ordovician period (505 million to 438 million years ago). Its distinctive appearance makes the genus a useful guide fossil for Ordovician rocks and time. The... daddy longlegs Opiliones any of more than 6,000 species of arachnids (class Arachnida) that are known for their extremely long and thin legs and for their compact bodies. Daddy longlegs are closely related to scorpions (order Scorpiones) but, because of their appearance,... Daphnia well-known water flea genus. decapod (order Decapoda), any of more than 8,000 species of crustaceans (phylum Arthropoda) that include shrimp, lobsters, crayfish, hermit crabs, and crabs.

The presence of five pairs of thoracic legs (pereiopods) is the basis for the name decapod (from the... Deiphon genus of trilobites (extinct arthropods) easily recognized in fossil form in Silurian rocks in North America because of its highly unusual shape (the Silurian Period began 438 million years ago and ended 408 million years ago). The pleural lobes (at... Dikelocephalus genus of trilobites (extinct arthropods) that is a useful guide fossil for the Late Cambrian rocks (512 to 505 million years ago) of Europe and North America. Dikelocephalus is distinguished by its broad head, its large and relatively well-developed... Dungeness crab (Cancer magister), edible crab (order Decapoda of the class Crustacea), occurring along the Pacific coast from Alaska to lower California; it is one of the largest and, commercially, most important crabs of that coast. The male is 18 to 23 centimetres...

fairy shrimp any of the crustaceans of the order Anostraca, so called because of their graceful movements and pastel colours. Some grow to 2.5 cm (about 1 inch) or more in length. They occur in freshwater ponds of Europe, Central Asia, western North America, the... false scorpion any of the 1,700 species of the order Pseudoscorpiones (sometimes Chelonethida) of the arthropod class Arachnida. They resemble true scorpions but are tailless and only 1 to 7.5 mm (0.04 to 0.3 inch) long. The chelicerae (first pair of appendages) bear... fiddler crab any of the approximately 65 species of the genus Uca (order Decapoda of the subphylum Crustacea). They are named “fiddler” because the male holds one claw, always much larger than the other, somewhat like a violin. Both claws in the female are relatively... fish louse any member of the crustacean subclass Branchiura, a group of parasites of migratory marine and freshwater fishes.

Of the approximately 120 known species, most belong to the genus Argulus. The fish louse has a very distinctive oval-shaped, flattened body... funnel weaver any of certain members of the spider family Agelenidae (order Araneida). Agelenids are notable for their funnel-shaped webs; they are a common group with many species that are distributed worldwide. The webs are built in the grass, under boards and rocks,... funnel-web spider Dipluridae family of spiders in the order Araneida that are named for their funnel-shaped webs. Their webs open wide at the mouth of the tube, and the spider sits in the narrow funnel waiting for prey to contact the web. When this happens, the spider... gammarid any member of the family Gammaridae, the largest of 80 or so families that make up the crustacean order Amphipoda. The name is sometimes also used to refer to amphipods of the genus Gammarus. The gammarid body is of basic amphipod shape: it is flattened...

garden spider Araneus diadematus a member of the orb weaver family Araneidae (order Araneida) characterized by white marks arranged in the form of a cross on the abdomen. A fairly common species, the garden spider occurs throughout the Northern Hemisphere and is often... ghost crab Ocypode any of approximately 20 species of shore crabs (order Decapoda of the class Crustacea). O. quadratus, the beach crabs noted for their running speed, occur on dry sand above the high-tide mark on the western Atlantic coast from New Jersey to Brazil.... giant crab (Macrocheira kaempferi), species of spider crab native to Pacific waters near Japan. It occurs at depths of 50 to 300 m (150 to 1,000 feet). The largest specimens may be up to 3.7 m or more from the tip of one outstretched claw to another. The body is...

giant water scorpion any member of the extinct subclass Eurypterida of the arthropod group Merostomata, a lineage of large, scorpion-like, aquatic invertebrates that flourished during the Silurian Period (444 to 416 million years ago). Well over 200 species have been identified... Greenops genus of trilobites (extinct arthropods) found as fossils in Middle and Upper Devonian deposits (the Devonian Period began about 416 million years ago and lasted about 56 million years). Easily recognized by its distinctive appearance, Greenops has a... gribble any of the approximately 20 species of wood-boring, marine crustaceans constituting the genus Limnoria, in the order Isopoda. They feed on algae, driftwood, and the submerged wood of docks and wharves and sometimes attack the nonwoody insulation of submarine... hermit crab any crab of the families Paguridae and Coenobitidae (order Decapoda of the class Crustacea).

These crabs use empty snail shells (e.g., whelk or periwinkle) or other hollow objects as a shelter for partial containment and protection of the body. Their... hooded shrimp any member of the order Cumacea (superorder Peracarida), a group of small, predominantly marine crustaceans immediately recognizable by their unusual body shape. The head and thorax are wide and rounded, in sharp contrast to the slender, cylindrical,... horseshoe crab Xiphosura common name of four species of marine arthropod (class Merostomata, subphylum Chelicerata) found on the east coasts of Asia and North America. Despite their name, these animals are not crabs at all but are related to scorpions, spiders, and... horseshoe shrimp any member of the marine crustacean subclass Cephalocarida (class Crustacea), named because of the curving, horseshoelike shape of the body. Only nine species are known, the first of which was described in 1955. A very primitive group, the horseshoe...

insect Insecta or Hexapoda any member of the largest class of the phylum Arthropoda, which is itself the largest of the animal phyla. Insects have segmented bodies, jointed legs, and external skeletons (exoskeletons). Insects are distinguished from other arthropods... isopod any member of the order Isopoda (class Crustacea), a group of diverse, widely occurring forms including marine, freshwater, and terrestrial species. Most are free-living, but a number of marine species are parasitic on other animals. They are usually... Isotelus genus of trilobites (extinct arthropods) restricted to Europe and North America during the Ordovician Period (about 488 million to 444 million years ago). Isotelus was relatively large for a trilobite and was characterized by its distinctive flat shape.... Jonah crab North American crab species (Cancer borealis) closely related to the Dungeness crab. jumping spider Salticidae any of more than 5,000 species of spiders (order Araneida) known for their ability to jump and pounce upon their prey.

They range in size from 2 to 22 mm (0.08 to 0.87 inch), although most are small to medium-sized. They are very common in... kelp crab Pacific species of spider crab. king crab (Paralithodes camtschaticus), marine crustacean of the order Decapoda, class Malacostraca. This edible crab is found in the shallow waters off Japan, along the coast of Alaska, and in the Bering Sea. The king crab is one of the largest crabs, weighing... krill any member of the crustacean order Euphausiacea or of the genus Euphausia within that suborder. Euphausiids are shrimplike marine animals that are pelagic in habit (i.e., they live in the open sea). They differ from true shrimp (order Decapoda) in that... land crab any crab of the family Gecarcinidae (order Decapoda of the class Crustacea), typically terrestrial, square-bodied crabs that only occasionally, as adults, return to the sea. They occur in tropical America, West Africa, and the Indo-Pacific region. All...

lobster any of numerous marine crustaceans (phylum Arthropoda, order Decapoda) constituting the families Homaridae (or Nephropsidae), true lobsters; Palinuridae, spiny lobsters, or sea crayfish; Scyllaridae, slipper, Spanish, or shovel lobsters; and Polychelidae,... lynx spider Oxyopidae any of several groups of active spiders (order Araneida) that do not build a nest or web but capture their prey by pouncing upon them. Lynx spiders are distributed worldwide and in North America are most common in southern regions. The eyes... malacostracan any member of the more than 29,000 species of the class Malacostraca (subphylum Crustacea, phylum Arthropoda), a widely distributed group of marine, freshwater, and terrestrial invertebrates. Lobsters, crabs, hermit crabs, shrimp, and isopods are all... mantis shrimp any member of the marine crustacean order Stomatopoda, especially members of the genus Squilla.

Mantis shrimps are so called because the second pair of limbs are greatly enlarged and shaped like the large grasping forelimbs of the praying mantid, or... millipede Diplopoda any member of the arthropod class Diplopoda, distributed worldwide and commonly grouped with several other classes as myriapods. The approximately 10,000 species live in and eat decaying plant matter; some injure living plants, and a few are... mite any of numerous species of tiny arthropods, members of the mite and tick subclass Acari (class Arachnida), that live in a wide range of habitats, including brackish water, fresh water, hot springs, soil, plants, and (as parasites) animals, including... mole crab Emerita, or Hippa, talpoida crab of the Atlantic beaches from New England to Mexico. It is so named from its digging mole-fashion in sand. The shell is about 3.75 centimetres (1.5 inches) long, somewhat egg-shaped and yellowish white with purplish markings....

mussel shrimp any of a widely distributed group of crustaceans belonging to the subclass Ostracoda (class Crustacea) that resemble mussels in that the body is enclosed within a bivalved (two-valved) shell. Mussel shrimp differ from most other crustaceans in having... mustache shrimp any member of the crustacean subclass Mystacocarida, a small group of primitive, free-living marine animals. Of the few species known, the first was discovered near Woods Hole, Mass., U.S., in 1943. The shrimp’s rather tubular body includes a long abdomen;... myriapod any member of several closely related groups of the invertebrate phylum Arthropoda, including the extinct Archipolypoda, extant Diplopoda, or millipedes (see millipede), Chilopoda, or centipedes (see centipede), Pauropoda (see pauropod), and Symphyla... nursery-web spider Pisauridae any member of a family of spiders (order Araneida) noted for the female spider’s habit of making a protective nursery web for the young and standing guard over that web.

Most species are medium to large in size, and many are found near the... ogre-faced spider any member of the family Dinopidae (or Deinopidae; order Araneida). One pair of eyes is unusually large, producing an ogrelike appearance. The spiders occur throughout the tropics. One genus, Dinopis, the net-casting spider, carries a web that is thrown... Olenellus genus of trilobites (extinct arthropods) common in but restricted to Early Cambrian rocks (542 million to 521 million years ago) and thus a useful guide fossil for the Early Cambrian. Olenellus had a well-developed head, large and crescentic eyes, and... opossum shrimp any member of the crustacean order Mysidacea. Most of the nearly 1,000 known species live in the sea; a few live in brackish water; and fewer still live in fresh water. Most are 1 to 3 cm (about 0.4 to 1.2 inches) long. The name opossum shrimp derives...

orb weaver any spider of the family Araneidae (Argiopidae or Epeiridae) of the order Araneida, a large and widely distributed group noted for their orb-shaped webs. More than 2,840 species in some 167 genera are known. Notable among them are the garden spiders... Paradoxides genus of trilobites (an extinct group of arthropods) found as fossils in Middle Cambrian rocks of North America and western Europe (the Cambrian Period lasted from about 542 million to 488 million years ago). Paradoxides has a well-developed head region... pauropod any member of the class Pauropoda (phylum Arthropoda), a group of small, terrestrial invertebrates that superficially resemble tiny centipedes or millipedes. The approximately 380 known species are found worldwide under dead leaves, stones, and rotten...

pea crab any member of a genus (Pinnotheres) of crabs (order Decapoda) living in the mantle cavity of certain bivalve mollusks, echinoderms, and polychaetes as a commensal (i.e., on or in another animal host but not deriving nourishment from it). Females of Pinnotheres... pentastomid any of about 100 species of tiny parasites belonging to the Pentastomida, now generally considered a subclass of the phylum Arthropoda. Pentastomids range from a few millimetres to 14 cm (about 6 inches) in length and lack respiratory, circulatory, and... Phacops genus of trilobites (an extinct group of aquatic arthropods) found as fossils in Silurian and Devonian rocks (between about 359 million and 444 million years old) in Europe and North America. Phacops is a common and easily recognizable form, with its...

Phillipsia genus of trilobites (an extinct group of aquatic arthropods) uncommonly found as fossils in Carboniferous and Permian rocks (about 251 million to 359 million years old) in Europe, North America, and the Far East. One of the last known trilobite genera,... pill bug any of the terrestrial crustaceans of the families Armadillididae and Armadillidae (order Isopoda). When disturbed, the pill bug rolls itself up into a tiny ball. Like the related sow bug, it is sometimes called the wood louse. For mollusks also known... pirate spider any member of the family Mimetidae (order Araneida), noted for its habit of eating other spiders. The approximately 100 species are distributed worldwide. They are characterized by a row of sharp bristles on the first pair of legs. Pirate spiders do... prawn any of certain crustaceans of the shrimp suborder Natantia. See shrimp. ray spider any spider of the family Theridiosomatidae (order Araneida), known for their conelike webs.

Most ray spiders are less than 3 mm (0.125 inch) in body length and are usually found near streams or in damp areas. The strands of the ray spider’s web extend... red crab Pacific crab species closely related to the Dungeness crab. red spider any of the plant-feeding mites of the family Tetranychidae (subclass Acari). Red spiders are a common pest on houseplants and agriculturally important plants, including the foliage and fruit of orchard trees. The life cycle of the red spider from egg... redback Latrodectus hasselti species of comb-footed spider (family Theridiidae) that is native to Australia, the females of which are venomous and distinguished by an orange or red stripe on the back of the abdomen. The body colour of males and females typically... robber crab Birgus latro large nocturnal land crab of the southwest Pacific and Indian oceans. It is closely related to the hermit crab and king crab. All are decapod crustaceans (order Decapoda, class Crustacea). Adult robber crabs are about 1 metre (about 40 inches)...

sac spider Clubionidae any member of a relatively common, widespread family of spiders (order Araneida) that range in body length from 3 to 15 mm (about 0.12 to 0.6 inch) and build silken tubes under stones, in leaves, or in grass. Chiracanthium inclusum, found... sand flea any of more than 60 terrestrial crustaceans of the family Talitridae (order Amphipoda) that are notable for their hopping ability. The European sand flea (Talitrus saltator), which is about 1.5 cm (0.6 inch) long, lives on sand beaches near the high-tide... scampi (Nephrops norvegicus), edible lobster of the order Decapoda (class Crustacea). It is widespread in the Mediterranean and northeastern Atlantic, from North Africa to Norway and Iceland, and as a gastronomic delicacy it is commercially exploited over much...

scorpion Scorpiones or Scorpionida any of approximately 1,500 elongated arachnid species characterized by a segmented curved tail tipped with a venomous stinger at the rear of the body and a pair of grasping pincers at the front. Although scorpions are most common... sea spider any of the spiderlike marine animals comprising the class Pycnogonida (also called Pantopoda) of the phylum Arthropoda. Sea spiders walk about on the ocean bottom on their slender legs or crawl among plants and animals; some may tread water. Most pycnogonids... sheet-web weaver Linyphiidae a rather common group of small spiders (order Araneida) numbering about 2,000 species worldwide. Most are less than 6 mm (1 4 inch) in length and are seldom seen. Their webs are flat and sheetlike and dome- or cup-shaped. The spider is usually... shrimp any of the approximately 2,000 species of the suborder Natantia (order Decapoda of the class Crustacea). Close relatives include crabs, crayfish, and lobsters.

Shrimp are characterized by a semitransparent body flattened from side to side and a flexible... Common Spider Crab - Chesapeake Bay Program Chesapeake Bay Program Common Spider Crab Libinia emarginata The shell of the common spider crab measures about four inches from front to back. When its legs are stretched out, the spider crab can reach a spread of one foot. (joo0ey/Flickr) Also known as the portly spider crab or the nine-spined spider crab, the common spider crab is a long-legged and slow-moving crustacean that covers itself in algae and small debris as a defense against predators. Appearance: The common spider crab has a khaki-colored, triangle-shaped carapace (shell) that measure about four inches front to back and features a median row of nine low spines (which differentiate the creature from the six-spined spider crab). Its shell is often ornamented with various spines and tubercles and clothed in algae, debris and small invertebrates held in place by hook-like hairs. When its legs are outstretched, the common spider crab can reach a spread of up to one foot, while males grow larger than females.

The crab has white, narrow claws that are slow and not very strong, and has a tapered snout and short eyestalks. Habitat: Found on a variety of ocean, bay or harbor bottoms, from shallow water to depths exceeding 150 feet. Range: Found from Nova Scotia to the western Gulf of Mexico; inhabits the brackish and salty waters of the Chesapeake Bay from Washington, D.C., to the Bay's mouth. Feeding: These crabs are sluggish and unaggressive scavengers with poor eyesight. Sensitive tasting and sensing organs located on the tips of its walking legs allow the common spider crab to identify food in the water or mud as it walks. It will often feed on large starfish. Predators: Spider crabs belong to a group known as "decorator crabs": the crab's main defense against predation is ability to camouflage itself with various spines and tubercles, algae, debris and small invertebrates. When startled, it will wave its pincers over its head in a warning gesture. Reproduction and Life Cycle: The common spider crab must molt to grow. When molting, this crab clings to top of eelgrass close to water's surface.

They have been observed molting in large "pods" in the fall, hibernating in dense patches in the winter and mating in large groups in the spring. Females close to releasing eggs are held behind males and aggressively protected. Young hatch from eggs that are bright orange-red when laid but turn brown during development, which takes about 25 days. Other Facts: Spider crabs are tolerant of polluted waters and eutrophic, or low-oxygen, environments. They often walk in a forward motion, although they are capable of side-stepping like other crabs. Sources and Additional Information:

Question: Which species of decapod has varieties called "fiddler', 'spider' and 'hermit'?
Answer: Crab